Preheat oven to 250°. In a large bowl, combine Corn Chex, Wheat Chex, and Teddy Grahams. In a small bowl, mix butter, brown sugar, cinnamon, salt, and vanilla.
Drizzle about one-third of butter mixture over Chex mixture. Toss to coat, then repeat with remaining butter mixture until every component is coated.
Divide Chex mixture between 2 unlined rimmed baking sheets; spread in an even layer.
Bake Chex Mix, tossing every 15 minutes, until toasted and crisp, 30 to 45 minutes.
Let cool, then mix in candy corn, pretzels, sweet potato chips, and Reese's pieces.
Notes
This scarecrow crunch recipe is so fun because you can change up any ingredients according to what you like! Chex Mix can be made 2 weeks ahead. Store in an airtight container at room temperature.